A new report found many of the vaccines for children are not properly stored, which could cause them to become less effective.

The office of the Inspector General visited 45 clinics in five areas of the country that ordered the most vaccine. They found three quarters of the medical practices stored vaccines at the wrong temperature for several hours. Many also kept a mix of expired and unexpired vaccines.

Experts say these vaccines may not provide maximum protection against diseases. The Center for Disease Control and Prevention is working with clinics to make sure vaccines are better managed.